How Your Pregnancy Diet Can Predict Baby's Birth Weight

When it comes to a baby's growth in utero, we like the Goldilocks principle: Not too big, not too little, but just right. Neither end of the weight spectrum is optimal when it comes to development of the brain and body, and having a baby that's either too heavy or too light is associated with many problems, both during pregnancy and beyond.

If a baby is too large, for example, not only are you more likely to need a Cesarean section, but your baby is also at higher risk for developing obesity or type II diabetes during childhood. Too small, and he may experience developmental problems.

Your prenatal weight gain helps forecast your baby's size: If you gain too much, there's a good chance he will, too, and vice versa. If you put on the recommended amount, there's no guarantee your baby will be born at a "proper" weight, but it's much more likely that he will.

How much you should gain depends largely on your pre-pregnancy body mass index, or BMI. Besides this, you want to watch out for big fluctuations—up or down. Steady weight gain throughout pregnancy is best (though you might not put on much in the first trimester).

How Much to Eat During Pregnancy

While you don't want to "diet" during pregnancy, quantity still counts. Right here, right now, let's make a deal to take the "eating for two" mantra and toss it into our conversational Diaper Genie, never to see, speak, hear or think it again.

The more accurate principle that pregnant women should follow is "eating for 1.1." Essentially, that means you need to eat only 10 percent more than the number of calories you needed to eat to maintain your weight before you were pregnant. Here's how that translates:

First Trimester: Shoot for an increase of about 100 calories per day more than your ideal pre-pregnancy calorie intake, or the equivalent of a glass of skim milk.

Second Trimester: You'll want an extra 250 calories per day, the equivalent of a mid-afternoon snack of 10 walnuts plus an apple.

Third Trimester: You'll need an extra 300 calories per day, the equivalent of three pieces of fruit. There will be days when, because of nausea or exhaustion, you won't feel like taking in these extra calories. As long as you're in the ballpark most of the time, that's fine.

Foods to Eat During Pregnancy

When choosing foods, remember that everything you put into your body is passed along to your baby through the placenta, so your calories should come from the purest and most nutrient-dense sources. The placenta is no Brita filter: It doesn't screen out the bad and only let the good pass through; it lets everything below a certain size through.

This means that any toxins that make the size cut can get passed to the fetus, including saturated and trans fats; mercury, pesticides and other toxins; sugar in all its forms; and chemical food additives. That said, here, in a nutshell, is what you should aim to eat daily, breaking up the total into six small meals:

• Nine or more servings of fruits and vegetables (organic if possible)
• Three or more servings of whole grains (for example, bread, cereals, brown rice)
• Three or more servings of lean protein in the form of lean meat, skinless poultry, low-fat dairy, low-mercury fish (trout and wild domestic salmon are good choices), eggs, nuts, peas, beans, lentils and tofu.

Keep eating this healthfully, and you—and your baby—will be just fine.